i) Construct the centre point O. Connect that point with A and C to form Triangle AOC.
OA = OC = 6 (Radii of circle)
Angle AOC = 30 (angle at the centre is twice the angle at the circumference)
Now simply use the cos rule to find AC.
ii) One way I see is using the sine rule to find the value of one of the other sides, then use the formula
to get the area.